Compact Zoom Lens with Inverted First Group for Dome Cameras
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Solution Overview
Problem
Existing zoom lenses for telephoto applications, particularly in dome monitoring cameras, face challenges in miniaturization while maintaining high performance, as they are difficult to reduce in size without compromising optical quality.
Innovation Solution
A four-group zoom lens system with a first group having positive, positive, and negative lenses, a second group with a cemented lens configuration, a third group with at least one positive and one negative lens, and a fourth group with aspheric surfaces, where the second and fourth groups move along the optical axis to correct image plane position and focusing, optimizing power arrangement and reducing lens length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the zoom ratio is reduced to decrease the total length of the lens, then the lens size is reduced, but the telephoto side power variation capability is compromised
Solution Approach 1:
The patent changes the refractive index parameters of the lenses, specifically using a positive lens with refractive index Nd>1.6 and a negative lens with refractive index Nd<1.6 in the first group, to achieve compact design while maintaining telephoto power variation capability. This parameter optimization allows the lens to achieve both size reduction and functional requirement
Solution Approach 2:
The patent employs composite lens design in the first group, combining lenses with different refractive index characteristics (Nd>1.6 and Nd<1.6) to create a compact optical system that maintains both wide-angle and telephoto performance, resolving the contradiction between size reduction and power variation capability
2Length of stationary object
If the lens is miniaturized for dome camera applications, then the lens size is reduced, but optical performance deteriorates
Solution Approach 1:
The patent applies local quality optimization by assigning specific refractive index ranges to specific lens positions - the first group uses positive lenses with Nd>1.6 and negative lenses with Nd<1.6, while subsequent groups have optimized refractive indices. This localized material selection maintains high optical performance in the compact lens structure
Solution Approach 2:
The patent divides the lens into four functional groups with distinct optical roles, where each group is further segmented into specific lens elements with optimized refractive indices. This segmentation allows independent optimization of each segment to maintain overall optical performance while reducing total lens size
3Device complexity
If the first group uses conventional lens arrangement, then the design is simpler, but the lens length increases
Solution Approach 1:
The patent inverts the conventional lens arrangement in the first group by placing a positive lens with high refractive index (Nd>1.6) followed by a negative lens with low refractive index (Nd<1.6), rather than the conventional sequence. This inverted arrangement with optimized refractive indices achieves compact lens length while maintaining manufacturability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in a small-sized, high-performance zoom lens capable of power variation on the telephoto side, effectively reducing lens length while maintaining excellent optical performance across the visible and near-infrared regions.
Implementation Method 1
The first group includes, in order from the object side, a first lens of the first group having a positive refractive power, a second lens of the first group having a positive refractive power and a third lens of the first group having a negative refractive power
Implementation Method 2
When a power of the zoom lens varies from a wide-angle end to a telephoto end, the second group is moved along an optical axis toward an image side with the first and third groups fixed
Implementation Method 3
the fourth group is moved along the optical axis to perform correction of a position of the image plane, which is associated with the variation of the power, and focusing
Implementation Method 4
a fourth group following the third group. The fourth group has aspheric surfaces
Implementation Method 5
the second and third lenses of the first group may form a cemented lens
Data Source
AI summary
A zoom lens includes, in order from an object side, a first group having a positive refractive power, a second group having a negative refractive power, a diaphragm, a third group having a positive refractive and a fourth group following the third group. When a power of the zoom lens varies from a wide-angle end to a telephoto end, the second group is moved along an optical axis toward an image side with the first and third groups fixed to the optical axis so as to vary the power and the fourth group is moved along the optical axis to perform correction of a position of the image plane, which is associated with the variation of the power, and focusing.